This invention relates generally to ski poles of the type used in downhill and cross-country skiing by both amateurs and skilled athletes, and more particularly to a ski pole having features intended to reduce the hazards of injury to the thumbs of the skier. Gamekeeper fracture of the thumb and Stener lesion are the second most common trauma of skiers. The ulnar collateral ligament is torn and the ends distracted allowing an aponeurosis to interpose itself between the torn ends of the ulnar collateral ligaments. This interposition prevents the normal healing of the ulnar collateral ligament and causes long term disability with disorders of pinch and grip. The damage occurs upon high impact collision between the ski pole and the thumb where the skier normally grips the pole. The damage occurs most frequently during falls or loss of balance events, when the ski pole is loosely held and is suddenly accelerated relative to the hand that holds it. Extension of the thumb occurs when there is loss of grip on the ski pole.
The Stener lesion is believed to be avoidable if the pole is firmly gripped by the skier""s hand when the fall or loss of balance occurs, and/or if the direction of the kinetic energy can be directed along a vector that is different from that which causes hyperabduction of the thumb. An important condition in the development of a situation that leads to such a hand injury is that the ski pole has become fixed at its pointed tip, either in the snow, under the ski blades, or in any other obstacle that may present itself on the skier""s path. While losing his balance and falling, the skier generally loses the tight grip on the pole handle, which is normal during skiing and thus creates the conditions for violent hyperabduction of the thumb.
The problem was recognized and a solution proposed in U.S. Pat. No. 4,229,016 to Wolf. Therein a mechanism allows the handle to pivot relative to the extended shaft of the ski pole when a certain force is applied to the handle relative to the pole shaft. The forces required to cause the handle to pivot may be pre-selected such that the handle hopefully pivots before the thumb is injured. The handle may later be restored to its longitudinal position and the pole is again in condition for use.
Three patents to Bujold, U.S. Pat. Nos. 6,070,907; 6,082,767; and 6,203,063, disclose a ski or hiking pole having an articulated handle. The handle pivots relative to the shaft under high bending stress. An internal spring mechanism restores the pole to its normal configuration when the stress is no longer present.
Fuji, U.S. Pat. No. 4,597,589, provides a handle that is pivotable to a right angle with the shaft so that a skier may push off with a greater force at the start of a downhill run. The handle pivots when the user presses a button on the handle and a spring returns the handle to its normal position when the button is released.
Kepple, U.S. Pat. No. 4,332,399, provides a ski pole with a shaft in two portions. The upper portion is connected to the lower portion by a coil spring that bends only under high bending forces. The handle may also be spring-connected to the top of the shaft.
Kepka, U.S. Pat. No. 3,797,845, provides an extended history of ski poles designed to lessen the dangers of injury. His particular construction provides a shaft in two portions that telescope on each other when axial force on either end exceeds a preselected value. The pointed tip can also telescope. The primary concern is with skier impalement by the pole, and bending and thumb injuries are not considered. In all embodiments, the pole returns to its original condition when axial forces are removed.
In spite of prior recognition of the problem, thumb injuries, as stated, remain as the second most common skier injury. It is suspected that many thumb injuries go unreported although the consequences can be serious and at times permanent.
Mechanisms proposed for incorporation in ski poles in the earlier patents were complex and presumably costly to produce. Applicant is unaware of any commercially available ski pole that incorporates safety features to protect against thumb injury. What is needed is a protective ski pole that reduces the likelihood of thumb injury in those situations as described above where the skier momentarily loosens his grip on the ski handle while the tip of the ski pole is fixedly engaged in the snow or in some unexpected obstacle.
Generally speaking, in accordance with the invention, a ski pole less likely to cause thumb injuries to a skier is provided. The ski pole has normal strength when the pole is normally gripped at its handle and has reduced strength, is weakened, when the handle is not gripped. It should be understood that the pole is not so weak as to impair its utility when the handles are not gripped. A skier skis normally and does not have to continuously squeeze the pole handles to prevent failure of the poles. The poles are intended to break or permanently bend when a pre-determined level of excessive force is applied, as may happen in the emergency situations described above.
The poles are provided with a weakened section along their length. Desirably, the pole will fail in bending at the weakened section in an emergency situation prior to injury of the thumb. Reinforcement is provided for the weakened section whenever the pole handle is conventionally gripped by the person, but there is no reinforcement when the grip is released. Thus the ski pole has available two levels of bending strength and the skier selects the operating level either by intent or instinct in an emergency by his/her grip on the ski pole handle.
In a preferred embodiment, the pole shaft is a hollow tube with a short circumferential segment of the tube wall having a reduced cross-section. When the handle is gripped, a piston or plug slidable within the tube is aligned to span the reduced cross-section and reinforce the pole at that region. When the handle is not gripped, the piston slides away from the reduced wall segment and reduces the strength of the pole. A button on the handle connects to the sliding piston by a rod, cable, hydraulics, pneumatics, etc. Alternatively, actuation of the button may initiate an electrical sequence that actuates a magnetic solenoid to move the reinforcing piston. The weakened portion of the pole may be a replaceable section so the pole is reusable, and a particular pole may be calibrated to fail in bending at a pre-selected force.
Accordingly, it is an object of the invention to provide an improved protective ski pole that is strong when in normal use and becomes weaker in bending in an emergency situation wherein the skier releases his tight grip on the pole handle.
A further object of the invention is to provide an improved protective ski pole that is simple in construction and has two states, a stronger state and a weaker state.
It is a further object of the invention to provide an improved protective ski pole that is maintained with readily replaceable parts so that it may quickly be returned to use after occurrence of an emergency event.
Still other objects and advantages of the invention will be apparent from the specification. The invention accordingly comprises the features of construction, combination of elements, an arrangement of parts, which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.